1. Field of the Invention
This invention relates generally to prosthetic devices and, more particularly, to an artificial prosthetic sphincter for surgical implantation, whereby to overcome the problem of incontinence. The present sphincter represents an improvement in the construction of a prosthetic sphincter so as to be characterized by a diametric occlusion geometry capable of occluding a lumen, such as the urethra, with greater efficiency, improved biocompatability, less complex implant surgery, and easier and more precise post-surgical occlusive pressure adjustment than that which has characterized prosthetic sphincters of the prior art.
2. Prior Art
As will be recognized by those skilled in the art, certain individuals, because of a disability or surgical procedure or other organic and/or phychogenic cause, do not possess adequate function or competence of various bodily organs or muscles so as to achieve natural sphincteric continence for controlling the involuntary passage of urine. Accordingly, many sphincteric mechanisms have been proposed for surgical implantation as part of a system to selectively occlude and relax a lumen, such as the urethra, for controlling the passage of material therethrough. However, most known sphincteric mechanisms are characterized by a common shortcoming. That is, once the implant surgery is completed, there is no readily available means (without necessitating additional surgery) to accurately and continuously adjust the occlusive pressures to be applied to the urethra, or other lumen, to achieve continence.
More particularly, because of the swollen and aggravated condition of edema of the urethral tissues during and for a period subsequent to surgery, the physician cannot be certain as to the normalized condition of the patient's urethra until post-operative edema has subsided. Therefore, the physician must estimate the required minimal occlusive force needed to achieve coaptation. As a consequence of such estimate, sphincteric mechanisms are often improperly fitted or selected, so that the maximum occlusive pressure capability of such mechanisms is insufficient to successfully achieve continence or the minimum occlusive pressure capability exceeds the pressure needed to achieve continence. Excessive occlusive forces are known to undesirably minimize arteriovascular blood flow to the urethra and thereby increase the possibility of ischemia and erosion to the delicate tissues.
Moreover, where conventional sphincteric mechanisms include occlusive force control means, such force control is usually accomplished in large, step-wise increments. Therefore, no artificial sphincters are known which are adapted to easily and accurately control or continuously vary the occlusive pressures needed to achieve continence, so that the sphincter may be percutaneously tailored to the individual needs of the patient on an ongoing basis without requiring additional surgery.
What is still more, many conventional sphincteric mechanisms are characterized by a circumferential occlusion geometry. It has been found, and as will be pointed out in greater detail below, that sphincters which apply circumferential occlusive pressures to occlude the urethra are comparatively inefficient and must generate considerably greater pressures to achieve minimal coaptive continence (relative to a diametric occlusion geometry, as is characteristic of the sphincter of the present invention). In addition, it is believed that circumferential occlusive forces tend to increase the susceptibility of the urethra to atrophy, erosion, and/or ischemia.